1. Field of the Invention
The present invention relates to a method for manufacturing a liquid discharge head, and more particularly relates to a method for manufacturing an ink jet recording head that discharges ink for printing of a recording medium.
2. Description of the Related Art
An example liquid discharge head for discharging a liquid is an ink jet recording head employed for an ink jet recording system.
Referring now to the ink jet recording head, one consistent existing demand, to facilitate the printing of images having improved visual qualities, is a reduction in the size of the liquid droplets that are emitted, and another is a manufacturing technique for the precise production of a structure having minute ink flow paths and ink discharge ports. As such a manufacturing technique, photolithography is superior in both precision and simplicity. Thus, a photosensitive resin is an appropriate material for an ink jet recording head, and generally, a material cured through cationic polymerization is especially appropriate because the ink resistance provided by such a material is superior to that provided by a material cured through radical polymerization.
Photolithographic methods for manufacturing ink jet heads are disclosed in U.S. Pat. No. 4,558,333 and U.S. Patent Application Publication No. 2006/0033784. According to the method disclosed in U.S. Pat. No. 4,558,333, first, an ink flow path pattern is formed, using a first photosensitive resin, on a substrate on which ink discharge energy generating elements are mounted. And then, a second photosensitive resin layer is adhered by being laminated to the ink flow path pattern, and thereafter, ink discharge ports are formed in the second photosensitive layer. According to the method disclosed in U.S. Patent Application Publication No. 2006/0033784, first, an ink flow path pattern is formed, using a first photosensitive resin, on a first substrate on which ink discharge energy elements are mounted. Then, a top plate (called an orifice plate), which is composed of a second photosensitive resin and has ink discharge ports, is deposited on a second substrate. Thereafter, the orifice plate is thermally bonded to the ink flow path pattern, and the second substrate is removed.
For an ink jet recording head constructed in accordance with this latter method, to facilitate the discharge of minute ink droplets with which to provide high-quality recording, there must be as little distance as possible between the ink discharge energy generating elements and the ink discharge ports. Thus, lowering the height of the ink flow paths is also necessary, as is reducing the sizes of ink discharge ports and those of ink bubbling chambers, which are inherent constituents of the ink flow paths and which contact the ink discharge energy generating elements. That is, for an ink jet recording head constructed in accordance with the above described method to discharge minute ink droplets, during the lamination of an ink flow path structural member on a substrate, the thickness must be closely monitored and controlled.
Furthermore, with the objective of performing a high-speed and stable ink discharge operation, it is preferable that ink flow paths, when formed, have an arbitrary three-dimensional shape and a height that is changed in the direction of the height of the substrate.
According to the manufacturing method described in U.S. Pat. No. 4,558,333, a photosensitive resin layer to be used as an orifice plate is formed as a dry film on a flexible film base, and therefore, the suitable materials available, from which to make a selection, are limited.
In addition, it is preferable that heat and pressure be employed to laminate on the substrate the dry film in which the ink flow path pattern is formed. However, when heat and pressure are used, the dry film in which the ink flow paths are formed may be deformed, and the resin may sag and enter ink flow paths, so that accurately shaping all the ink flow paths will be difficult.
Further, the dry film used to provide an orifice plate must be thin and even in order to reduce the thickness of the ink flow path structure member. However, it is difficult to form a thin dry film by general coating means. Even if a thin dry film is deposited, it would be very difficult to bond the thin dry film to a substrate bearing the ink discharge energy generating elements and the ink discharge pattern, because a thin-film orifice plate will be fragile.
According to the manufacturing method described in U.S. Patent Application Publication No. 2006/0033784, when an orifice plate is to be bonded to a substrate on which ink discharge energy generating elements are mounted and ink flow paths are formed, a limitation is imposed on the accuracy of the alignment of the ink discharge energy generating elements and the ink flow path pattern with the ink discharge ports. That is, an undesirable manufacturing variance is quite easily generated that affects the discharge characteristics of an ink jet recording head.
In addition, because of the simplicity of the bonding process, thermal adhesion of the photosensitive resins is appropriate. However, when a negative photosensitive resin is employed, this resin has already been cured by the time photolithography is employed to form the ink discharge ports and the ink flow paths. Therefore, when negative photosensitive resins are to be adhered thereafter, an extremely high temperature may be required; either this, or the performance of the thermal adherence process may itself be difficult.